1. Field of the Invention
The present invention relates to antennas and, more particularly, pivotable antennas.
2. State of the Art
In electrical devices that require antennas, such as radios and the like, high frequency electrical signals must be conducted from the antenna to grounded electrical equipment, usually mounted on a printed circuit board (PCB) inside of a casing. Antennas that pivot from a closed position to an open position are increasing popular in such devices. In these electrical devices, it is necessary to minimize interference with the high frequency signal as it is transmitted from the antenna to the electrical equipment.
The equipment for conducting the high frequency signals from the antenna to the electrical equipment that is believed to be the one most commonly used today is shown schematically in FIG. 1. An antenna 21 is mounted on a conductive shaft 23 that is pivotable relative to a casing 25 in which electrical equipment such as a PCB 27 is mounted. A flexible, conductive finger 29 is grounded, usually soldered, to the PCB and extends outside of the shielded casing 25 and contacts the shaft 23. A shielded trace 31 inside of the casing 25 connects the finger 29 to the rest of the electrical equipment. The disadvantages of this conventional technique include the need for multiple interconnected elements between the antenna and the electrical equipment, such as the shaft, the finger, the trace, etc. The connections between these elements permit dissipation of the signal, and shielding of the elements is difficult and space consuming.
The inventor has recognized that it would be desirable to use a coaxial cable as all or part of the link between the antenna and the electrical equipment to minimize interference with the high frequency signal. Coaxial cables typically comprise a central conductor, a dielectric material around the conductor, a shielding material, usually braided wires, around the dielectric material, and a jacket, usually plastic, around the shielding material.
However, one problem that has been encountered with pivotable antennas, is the difficulty of attaching a delicate coaxial cable to an antenna that pivots. The torsional forces that are created upon pivoting the antenna often tend to be too great for the delicate cable. Accordingly, it is desirable to provide a pivotable antenna assembly that minimizes the effects of torsional forces in a coaxial cable when an antenna pivots relative to a portion of an attached coaxial cable.